How Does Black Mold Spread?

Spores

• Black mold is a cellular organism that exists in dry form as a spore. Because these spores are tiny -- invisible to the naked eye -- they are easily picked up by the wind and transported. Spores attach to people, animals, clothing and other items via cellular legs called hyphae, which are similar in appearance to the seeds of dandelion flowers. Mold spores enter indoor environments through doors, windows, building holes and cracks, and through heating, air conditioning and ventilation systems with outdoor air intakes.

Food Source

• For black mold to spread, it needs a food source. Materials with a high cellulose content, particularly wood, are particularly conducive to mold growth. Black mold also favors bathroom and ceiling tiles, cardboard, wallboard, wallpaper and paper covering on insulated pipes. Other food sources for mold are insulation, carpeting and fabric made of natural fibers such as cotton, dust, paints and upholstery.

Moisture

• Black mold spores that land on food sources remain dormant unless a sufficient amount of moisture is produced. Air temperature doesn't matter, as black mold grows equally well in cold or warm conditions. The crucial factor affecting growth is humidity or a constant supply of water. If an area has constant relative humidity of 55 percent or higher, then a mold problem is bound to occur. Once mold spores find ideal growth conditions, they begin multiplying within 24 to 48 hours. Areas with leaks or other types of water damage such as catastrophic flooding also initiate mold growth. Unless the water source is constant, however, black mold lacks the optimal conditions needed to keep spreading.

Growth Areas

• Any area that is dark with high relative humidity is a prime location for black mold growth. Wall cavities, both under and beneath drywall, are typical locales. Signs of infected walls include cracked and peeling paint, bulging and discoloration of the wall itself. Areas behind floor baseboards, which accumulate dirt and other nutrients, is another location for growth. Damp basements and crawl spaces, particularly where there is a high concentration of wood or wood products, are also prime breeding grounds for black mold.